1. Field of the Invention
This invention relates to extension bars for socket wrenches and particularly to extension bar for socket wrenches having improved torque characteristics.
2. Description of Related Art
Socket wrenches have been in use for many years. Extension bars are a common accessory frequently used with socket wrenches. Because of the shape of the socket wrenches, they often can not reach into narrow or confined spaces. The extension bar is then used to project the socket itself into the confined space. Typically, these bars are actually round shafts of metal. Often the shafts are solid, having an opening for the socket wrench on one end and a post to receive the socket at the other end. Sometimes, the extension bars are hollow shafts that have the post on one end and a flared end at the other end to receive the socket wrench. In both cases, these extensions suffer from one major flaw. The shafts twist when torque is applied. Therefore, in many cases, considerable force must be applied to the wrench to overcome this twisting of the extension bar before force is applied to the bolt or nut to be loosened. This twisting becomes more pronounced as the length of the extension bar increases. For extreme lengths of extensions (three or four feet), the amount of twist may be so great that it is virtually impossible to impart force on the nut. The shaft of the extension simply absorbs all the torque that is applied by the wrench.
FIG. 1 shows a free body diagram of a typical extension bar 100 as prior art. A socket wrench 101 applies a rotational force F onto the shaft. The extension bar 100 is shown rotating about the central axis. Socket 102 is shown remaining stationary even though the force is being applied to the shaft. The socket 102 remains stationary until the twist in the shaft is fully absorbed. At that point, torque can be transmitted to the socket head to work a fastener (not shown).